The present invention relates to a noise insulation structure of an automotive vehicle, which insulates a noise transmitted to a vehicle inside from a floor face of the vehicle, for example.
There are various noises which occur outside the vehicle during a vehicle traveling, such as a noise generated by a sliding tire on a road surface, a noise radiated from an internal combustion engine or a transmission, or a noise generated by traveling air following outside the vehicle.
There is a concern that in a case in which the above-described noises occurring outside the vehicle are transmitted to the vehicle inside from a floor panel constituting the floor face of the vehicle as a transmitted sound, for example, the comfortability for a passenger may be deteriorated by this transmitted sound. Accordingly, the superior noise insulation to suppress the transmitted sound is required to the automotive vehicle.
U.S. Pat. No. 6,685,250, for example, discloses a noise insulation structure in which a urethane layer, a lower mass layer, a low-resilient urethane layer, an upper mass layer, and a carpet are overlapped in order from below and placed on a steel-made vehicle floor plate which constitutes the floor face of the vehicle. This disclosed structure can constitute a two-degree of freedom-system noise insulation structure, which can secure the high noise insulation superior to a one-degree of freedom-system noise insulation structure.
Meanwhile, Japanese Patent Laid-Open Publication No. 2008-285026 discloses a structure in which a multilayer carpet is placed on a floor panel having a downward recess. This multilayer carpet comprises a spacer arranged in the recess, a sound-absorbing felt material, a noise-insulating sheet, a sound-absorbing felt material and a skin material, which are overlapped in order from below. This disclosed structure can uniform the sinking amount for a pressing load even in a case in which the floor panel has the recess, and secure the superior noise insulation for the noises occurring outside the vehicle.
According to the above-described disclosed multilayer noise insulation structures, however, the number of parts for the noise insulation increases, so that there is a concern that the weight and costs of the vehicle may improperly increase.